EP3944890A1 - Method and system for pretreatment of gaseous effluent for capturing post-combustion co2 - Google Patents

Abstract

The present invention relates to the field of capturing CO₂ from a gaseous effluent. Combustion of the inlet gaseous effluent is carried out with a fuel, so as to obtain a hot gaseous effluent rich in acid compounds and the hot gaseous effluent rich in acid compounds is cooled to obtain a cold effluent rich in acid compounds, which is subsequently used in the contacting step with an absorbent solution rich in acid compounds.

Description

Technical area

• précombustion : concerne la captage avant la combustion industrielle,
• postcombustion : concerne la captage après la combustion industrielle classique (à l'air), avec peu ou pas de modification du procédé de combustion,
• oxycombustion : concerne la captage après une combustion à l'oxygène pur.

The present invention relates to the field of capturing CO ₂ from a gaseous effluent. The CO ₂ capture process that can be included in a method of the CSC type (from the English term CCS - for Carbon Capture and Storage) consists in trapping the CO ₂ molecules before, during or after the industrial combustion stage in order to prevent its release into the atmosphere and thus control the emission of greenhouse gases. Three families of capture processes are thus envisaged:

• pre-combustion: concerns capture before industrial combustion,
• post-combustion: concerns capture after conventional industrial combustion (in air), with little or no modification of the combustion process,
• oxycombustion: concerns capture after combustion with pure oxygen.

The present invention relates to post-combustion capture.

Among the solutions to reduce CO ₂ emissions, CO ₂ Capture and Storage (CCS) technologies are being developed, which can be used by industrial emitters. These CCS technologies are essential to be able to achieve the objectives set at the Paris Climate Conference in December 2015 (COP21). These technologies will have to contribute 12% to the reduction of CO2 emissions in 2050 if we want to limit global warming to 2°C by 2100. In response to the need for CO ₂ capture in post-combustion, various high-performance technologies are in development course. Currently, the most promising technologies for the capture of CO ₂ in fumes and industrial gases are absorption technologies using solvents. Most of the solvents used can degrade in the presence of oxygen. For optimal use of the process, the oxygen concentration in the fumes or industrial gases must be minimized.

• le procédé de production d'une cimenterie produit des quantités importantes de CO₂,
• l'énergie à mettre en œuvre pour le captage du CO₂ est très importante, équivalente à celle mise en œuvre pour faire fonctionner le procédé de production,
• les fumées de combustion sont riches en CO₂
• les fumées sont riches en oxygène O₂.

As part of the prospective on the CO ₂ theme, the case of application in cement works, metallurgical sites, and similar industrial sites, for example the production of lime, shows an interest, in particular for the following problems:

• the production process of a cement plant produces significant quantities of CO ₂ ,
• the energy to be used for CO ₂ capture is very high, equivalent to that used to operate the production process,
• combustion fumes are rich in CO ₂
• the fumes are rich in oxygen O ₂ .

In the case of the use of CO ₂ capture processes by absorption using solvents, this last point is critical because it can impact the degradation of the solvent and therefore the operating costs of the process since it is necessary to replace the volume of solvent more often. Indeed, the deacidification of gaseous effluents, such as for example natural gas and combustion fumes, is generally carried out by washing with an absorbent solution. The absorbent solution makes it possible to absorb the acid compounds present in the gaseous effluent (H ₂ S, mercaptans, CO ₂ , COS, SO ₂ , CS ₂ ).

However, it is well known to those skilled in the art that the amines which can be used as solvent have the disadvantage of degrading under the conditions of implementation. In particular, amines can be degraded by oxygen causing consumption of the amine and the formation of degradation products which accumulate in the unit or, for the most volatile, which are entrained in the gaseous effluents of the process. . Thus, in particular in the case of post-combustion flue gas treatment, in a process using an aqueous solution of monoethanolamine (MEA), large quantities of ammonia can be formed. The ammonia thus formed is entrained in the atmosphere with the treated fumes, which poses problems as regards the protection of the environment.

Another problem considered in the context of the CO ₂ capture process, and in particular the postcombustion capture processes by absorption, is the need to produce low or medium pressure steam for the solvent regeneration phase. The cost of captured CO ₂ will depend greatly on the amount of steam needed and the cost of this steam. In sites where residual vapor recovery from the industrial process is not possible or insufficient to supply the needs of the process, the cost of CO ₂ will increase significantly.

Prior technique

The relevant prior art consists of post-combustion CO ₂ absorption processes for the capture of CO ₂ . Three processes are particularly interesting: Hicapt ^™ Hicapt+ ^™ and DMX ^™ (IFP Energies nouvelles, France). The HiCapt+ ^™ process includes additives to combat solvent degradation by oxygen.

FR2948578 discloses a Hicapt+ ^™ process comprising an absorbent solution containing a degradation inhibitor derived from a triazole or a tetrazole, and a process for absorbing acid compounds contained in a gaseous effluent.

EP2228119A1 unveils a Hicapt+ ^™ process implementing the deacidification of a gas using an absorbent solution with an optimized water washing section.

EP1656983A1 unveils a DMX ^™ process, which offers the deacidification of a gas with an absorbent solution with fractional regeneration.

In addition, the level of residual oxygen present in the industrial combustion fumes reduces the service life, by accelerating the degradation of the solvent, which therefore impacts the operating costs of the process since the solvent must be replaced more often.

Summary of the invention

The present invention proposes a method and a system for reducing the degradation of an absorbent solution used to absorb the acid compounds contained in a gaseous effluent, the absorbent solution comprising amines in aqueous solution. For this, the invention aims to reduce the level of oxygen contained in the treated fumes.

The present invention relates to a process for deoxidizing fumes or industrial gases before capturing CO ₂ by producing steam. This invention makes it possible to a) reduce the O ₂ concentration in the fumes and, optionally, b) produce steam which is used in the solvent regeneration phase to limit the energy input for the solvent regeneration phase .

In the present invention, it is proposed to eliminate the oxygen in the fumes by burning a fuel having as oxidizer the fumes rich in oxygen. The amount of oxygen, and therefore oxidizer, available in the fumes is sufficient to provide the necessary regeneration energy (from one third to all depending on the O ₂ content in the fumes), hence the interest of exploit this interesting synergy.

• On met en contact, dans une unité de séparation, un effluent gazeux froid et riche en composés acides avec une solution absorbante pauvre en composés acides de manière à obtenir un effluent gazeux pauvre en composés acides et une solution absorbante riche en composés acides,
• On régénère au moins une fraction de la solution absorbante riche en composés acides dans une colonne de régénération de manière à obtenir une solution absorbante pauvre en composés acides et un effluent riche en composés acides, ladite solution absorbante pauvre en composés acides étant utilisée dans l'étape de mise en contact avec ledit effluent froid et riche en composés acides,
• le procédé de séparation comporte en outre les étapes suivantes de désoxydation de l'effluent gazeux d'entrée :
  • On réalise une combustion, dans un dispositif de combustion, de l'effluent gazeux d'entrée avec un combustible, de manière à obtenir un effluent gazeux chaud et riche en composés acides,
  • On refroidit l'effluent gazeux chaud et riche en composés acides dans un échangeur et on obtient l'effluent froid et riche en composés acides utilisé dans l'étape de mise en contact avec une solution absorbante pauvre en composés acides.

The invention consists of a method for separating at least one acid gas contained in an inlet gaseous effluent containing at least the following steps:

• A cold gaseous effluent rich in acid compounds is brought into contact, in a separation unit, with an absorbent solution poor in acid compounds so as to obtain a gaseous effluent poor in acid compounds and an absorbent solution rich in acid compounds,
• At least a fraction of the absorbent solution rich in acid compounds is regenerated in a regeneration column so as to obtain an absorbent solution poor in acid compounds and an effluent rich in acid compounds, said absorbent solution poor in acid compounds being used in the step of bringing into contact with said cold effluent rich in acid compounds,
• the separation process also comprises the following stages of deoxidation of the inlet gaseous effluent:
  • Combustion is carried out, in a combustion device, of the inlet gaseous effluent with a fuel, so as to obtain a hot gaseous effluent rich in acid compounds,
  • The hot gaseous effluent rich in acid compounds is cooled in an exchanger and the cold effluent rich in acid compounds used in the step of bringing it into contact with an absorbent solution poor in acid compounds is obtained.

According to one embodiment, it is possible to control the quality of the hot effluent and rich in acid compounds with the addition, in the combustion device, of at least one auxiliary oxidizer.

According to one embodiment, a fluid in high pressure liquid form can be introduced into the exchanger to cool the hot gaseous effluent rich in acid compounds from which a fluid in high pressure vapor form is withdrawn. Preferably, said fluid can be used in the form of high pressure vapor as a source of energy for operating the regeneration column.

According to one embodiment, it is possible to control the quality of the operation of the regeneration column with the addition of a complementary fluid in the form of make-up high-pressure vapor.

According to one embodiment, a step can be introduced which consists in reheating the inlet gaseous effluent before introducing it, in the form of hot inlet effluent into the combustion device.

According to one embodiment, the inlet gaseous effluent can be reheated by introducing it into an exchanger from which it emerges in the form of hot inlet gaseous effluent.

According to one embodiment, it is possible to use the hot gaseous effluent rich in acid compounds at the outlet of the combustion device to reheat the inlet gaseous effluent.

According to one embodiment, the inlet gaseous effluent may be smoke resulting from prior combustion, in particular from an industrial process.

According to one embodiment, the effluent rich in acidic compounds can be stored underground, in particular in depleted or depleted oil or gas fields or in deep saline aquifers, or used to produce molecules of interest , for example platform molecules for chemistry.

According to one embodiment, the fuel can be waste rebus or biomass.

According to one embodiment, said at least one auxiliary oxidant can be dioxygen O ₂ .

According to one embodiment, said at least one acid gas may comprise at least one of the compounds including carbon dioxide CO ₂ .

According to one embodiment, the absorbent solution rich in acid compounds and the absorbent solution poor in acid compounds can be two states of an identical solvent comprising an amine solution with reactive compounds in aqueous solution, said two solutions containing more or less acidic compounds.

The invention also consists of a system for separating at least one acid gas contained in an inlet gaseous effluent capable of implementing the method of the invention.

Other characteristics and advantages of the method according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the appended figures and described below.

List of Figures

• The figure 1 illustrates a combustion diagram according to the state of the art.
• The picture 2 illustrates a combustion diagram according to a first embodiment of the invention.
• The picture 3 illustrates a combustion diagram according to a second embodiment of the invention.

Description of embodiments

The figure 1 presents a diagram of a method for separating at least one acid gas contained in a gaseous effluent according to the state of the art. We consider an industrial combustion inlet gaseous effluent (for example smoke, industrial gas, etc.) (100) which may contain oxygen in the form of dioxygen (O ₂ ). O ₂ can be present in the smoke or industrial gas because during industrial combustion it can be in excess to ensure both the industrial combustion completion and temperature control. Oxygen can also come from leakage of ambient air towards the flue gas line insofar as the combustion devices are generally operated in depression for reasons of safety vis-à-vis their environment. This combustion effluent can come from the combustion of fossil, synthetic or natural carbonaceous materials (transformed or not). This combustion effluent thus usually contains a substantial content of acid compounds (in particular H ₂ S, mercaptans, CO ₂ , COS, SO ₂ , CS ₂ ), for example carbon dioxide (CO ₂ ) resulting from the combustion. In the remainder of the description, only the case of carbon dioxide is described, but the process applies to all types of acid compounds (for example H ₂ S, mercaptans, CO ₂ , COS, SO ₂ , CS ₂ ). This CO ₂ is absorbed in the separation unit (1001), also called an absorber. The effluent poor in acid compounds (200) from the separation unit (1001) is a smoke whose CO ₂ content will have been significantly lowered. The separation unit (1001) performs a CO ₂ separation function by adsorption or by absorption. In the case of CO ₂ separation using an amine-based solvent, this absorber is a gas/liquid contactor which brings the inlet gaseous effluent to be treated (100) into contact with a solution liquid absorbent poor in acid compounds (501), also called an amine solution. This amine solution takes on CO ₂ within the separation unit (1001). The solution obtained is an absorbent solution rich in acid compounds (500), rich in CO ₂ , which is sent to a regeneration column (1002), also called regenerator. The function of the regenerator is to extract the CO ₂ contained in the effluent rich in acid compounds (500), to form a gas outlet (700) comprising the CO ₂ extracted. This regeneration can be obtained by thermal effect and lowering of the partial pressure of CO ₂ in the gas phase at equilibrium with the amine solution in the regenerator. The hot utility (400) LP (low pressure) or MP (medium pressure) can be used to carry out the regeneration, for example by means of a reboiler (not represented). The regenerated amine solution (501) is called poor amine. It is sent to the absorber (1001) to capture CO ₂ .

• On met en contact, dans une unité de séparation (1001), un effluent gazeux froid et riche en composés acides (120) avec une solution absorbante pauvre en composés acides (501) de manière à obtenir un effluent gazeux pauvre en composés acides (200) et une solution absorbante riche en composés acides (500),
• On régénère au moins une fraction de la solution absorbante riche en composés acides (500) dans une colonne de régénération (1002) de manière à obtenir une solution absorbante pauvre en composés acides (501) et un effluent riche en composés acides (700), ladite solution absorbante pauvre en composés acides (501) étant utilisée dans l'étape de mise en contact avec ledit effluent froid et riche en composés acides (120),
• On réalise une combustion, dans un dispositif de combustion (2000), de l'effluent d'entrée (100) avec un combustible (300), de manière à obtenir un effluent gazeux chaud et riche en composés acides (110), et
• On refroidit l'effluent gazeux chaud et riche en composés acides (110) dans un échangeur (3000) et on obtient l'effluent froid et riche en composés acides (120) utilisé dans l'étape de mise en contact avec une solution absorbante pauvre en composés acides (501).

The invention consists of a method for separating at least one acid gas contained in an inlet effluent (100) comprising at least the following steps:

• In a separation unit (1001), a cold gaseous effluent rich in acid compounds (120) is brought into contact with an absorbent solution poor in acid compounds (501) so as to obtain a gaseous effluent poor in acid compounds (200 ) and an absorbent solution rich in acid compounds (500),
• At least a fraction of the absorbent solution rich in acid compounds (500) is regenerated in a regeneration column (1002) so as to obtain an absorbent solution poor in acid compounds (501) and an effluent rich in acid compounds (700), said absorbent solution poor in acid compounds (501) being used in the step of bringing into contact with said cold effluent rich in acid compounds (120),
• Combustion is carried out, in a combustion device (2000), of the inlet effluent (100) with a fuel (300), so as to obtain a hot gaseous effluent rich in acid compounds (110), and
• The hot gaseous effluent rich in acid compounds (110) is cooled in an exchanger (3000) and the cold effluent rich in acid compounds (120) used in the step of bringing it into contact with a poor absorbent solution is obtained. into acidic compounds (501).

The contacting steps in the separation unit (1001) and regeneration can be in accordance with the process according to the prior art, in particular as described in relation to the figure 1 . The steps of combustion and cooling of the hot gaseous effluent are steps of deoxidation of the inlet gaseous effluent (100).

The description of the picture 2 describes, in a non-limiting manner, the method according to a first embodiment of the invention and including several embodiment options. These implementation options can be considered independently of each other. In this figure, there is an inlet gaseous effluent (100), also called combustion smoke, which is treated here in the combustion device (2000). The function of the combustion device (2000) is twofold. The primary function of this combustion device (2000) is to lower the O ₂ content of the smoke (100) so as to reach a value compatible with the operation of the amine chosen to operate the separation unit ( 1001) and the regeneration column (1002). The second function of this combustion device (2000) is to increase the energy content of the combustion smoke (100) by a significant rise in its temperature.

These two functions are provided by the combustion of a fuel or a fuel mixture (300). This carbonaceous charge may be the same as that whose industrial combustion led to the formation of the inlet gaseous effluent (100) or another.

According to one embodiment of the invention, the fuel (300) can be waste scrap or biomass. Thus, in the context of reducing the environmental footprint, this load may be, for example and without limitation, industrial waste or scrap from a waste or biomass recovery center such as forest residues, by-products of agriculture or energy crops. In the latter case of biomass, the fact of capturing CO ₂ downstream leads to the accounting of negative emissions and this is particularly favorable in terms of the balance sheet of greenhouse gas emissions. Another fuel that can have a positive effect on emissions is hydrogen. Indeed, it is a fuel with high energy value and the product of its combustion, water, can be recovered directly and simply separated from the fumes. Moreover, it is an interesting way of hybridizing processes between fuel and electricity, the latter being easily recoverable in hydrogen by means of devices such as electrolyzers. This hybridization offers the advantage of being flexible depending on the quantity of carbon-free electricity available on the networks, in excess or not.

This combustion results in a hot effluent rich in acid compounds (110), the oxygen content of which can be brought below the threshold recommended by the amine-based solvent supplier, i.e. generally below 10% dry basis, and preferably below 6% dry basis.

If necessary, for example a lack of oxidizer which does not make it possible to achieve by combustion the supply of the energy required for regeneration, according to one embodiment, an air make-up (600) can be used. Indeed, according to one embodiment, the quality of the hot effluent rich in acid compounds (110) can be controlled with the addition, in the combustion device (2000), of at least one auxiliary oxidizer (600). According to one embodiment of the invention, said at least one auxiliary oxidant (600) can be dioxygen O ₂ .

This hot effluent rich in acid compounds (110) is cooled in a heat exchange device (3000) so as to produce a high pressure vapor fluid (410), also called hot utility, at the temperature and in sufficient quantity to regenerate the amine containing the CO ₂ captured from an absorbent solution rich in acid compounds (500) from the fluid in high pressure liquid form (800). Indeed, according to one embodiment of the invention, the method can also comprise a step which consists in introducing a fluid in high pressure liquid form (800) into the exchanger (3000) from which a fluid in high pressure vapor form is withdrawn. pressure (410), which can also be identified under the name of fluid in pressurized vapor form. In other words, within the exchanger (3000) the fluid in high pressure liquid form (800) recovers calories from the hot effluent rich in acid compounds (110) to form a hot utility (410) and an effluent rich in acid compounds (120), which comes out cooled.

According to one embodiment of the invention, said fluid in the form of high pressure vapor (410) can be used as a source of energy to operate the regeneration column (1002). The use of the fluid in the form of high pressure vapor (410) as a source of energy to operate the regeneration column (1002) is particularly useful in the sense that the condensation of this vapor in the reboiler makes it possible to transmit the heat efficiently to the process. By way of non-limiting example, said fluid in the form of high pressure vapor (410) can be a saturated vapor whose dew point is defined on the order of 10 to 20° C. above the operating temperature. of the reboiler intended for the regeneration of the amine solution. Thus, in the case of a solution of MEA at 30% by weight in water, one can typically have an operation at 120° C., that is to say a supplied vapor whose dew point is 140° C. The make-up air (600) can be used (within the limit of what is acceptable by the sizing of the unit in terms of flow rate and temperature, in particular in the case of adaptation of a capture of CO ₂ on an existing installation) to increase the amount of fuel that can be burned to produce the hot effluent rich in acid compounds (110) in order to increase the energy content of the high pressure vapor fluid (410).

According to one embodiment, this energy input can also be supplemented by an external energy input in the form of a make-up high-pressure vapor fluid (401). Indeed, according to one embodiment of the invention, it is possible to control the quality of the operation of the regeneration column (1002) with the addition of a complementary fluid in the form of make-up high pressure vapor (401).

Indeed, the oxygen content of the inlet gaseous effluent (100) is not always sufficient to carry out the combustion of a quantity of fuel sufficient to regenerate the quantity of solvent corresponding to all of the CO ₂ that we want to capture. By way of example, this is typically the case for a solvent of the MEA type of fumes containing more than 20% CO ₂ and less than 5% O ₂ on a dry basis. This make-up in the form of the make-up high-pressure vapor fluid (401) can then be predominant without losing the benefit of having an energy contribution from the utility in the form of the high-pressure vapor fluid (410). In general, care is taken, when possible, to pool the production systems of hot utilities as much as possible in the form of the high pressure vapor fluid (401) and in the form of the high pressure vapor fluid (410) so to optimize the energy balance of the whole, this can for example correspond to a partial heating of the fluids used to produce high pressure vapor fluid (401) on the path of the fumes between the inlet gaseous effluent (100) and the effluent poor in acid compounds (200) and in particular in the heat exchange device (3000) (not shown). In the exchanger (3000), the primary function is, by heat exchange on the heated flow in the form of the hot effluent rich in acid compounds (110), to produce the hot utility in the form of the vapor fluid high pressure (410). It is also possible to find in the exchanger (3000) additional heat exchangers to produce a stream in the form of the cold effluent rich in acid compounds (120) whose temperature is compatible with the optimal operation of the amine chosen, typically below 50° C. for a 30% by weight solution of MEA amine in water.

According to one embodiment of the invention, the method may also comprise a step which consists in reheating the inlet gaseous effluent (100) before introducing it, in the form of hot inlet effluent (101) into the combustion device (2000).

Preferably, the inlet gaseous effluent (100) can be reheated by introducing it into an exchanger (3000) from which it emerges in the form of hot inlet effluent (101).

The picture 3 represents a second embodiment of the invention, which comprises an additional step with respect to the embodiment of the figure 2 , heating of the effluent rich in CO ₂ , inlet gaseous effluent (100) in an exchanger (3000) in order to produce the stream in the form of the hot inlet gaseous effluent (101), the temperature of which is chosen to facilitate ignition fuel (300) in contact with the oxygen contained in the hot inlet gaseous effluent (101). Typically, for a known partial pressure of oxygen and a concentration of a determined fuel, it is possible to define a self-ignition point which can be an element making it possible to define the minimum temperature to reach the flow of the gaseous effluent from hot inlet (101) to achieve complete combustion of the fuel (300). This minimum temperature can also be lowered by implementing devices such as catalytic burners. The preheating of the inlet gaseous effluent (100) into hot inlet gaseous effluent (101) can be carried out by heat exchange with a dedicated hot utility (not shown), by thermal integration with the the auxiliary hot utility in the form of auxiliary high pressure vapor fluid (401) if necessary (not shown) or by integration in effluent load around the combustion device (2000) as a dedicated heat exchange zone of the heat exchange device (3000) as shown in the picture 3 . For this last variant embodiment, within the exchanger (3000), the fluid in high-pressure liquid form (800) as well as the inlet gaseous effluent recover calories from the hot effluent rich in acid compounds ( 110) to form a hot utility (410), a hot inlet gaseous effluent (101) and a cold, acid-rich effluent (120). In other words, the hot gaseous effluent rich in acid compounds (110) at the outlet of the combustion device can be used to heat the gaseous effluent at the inlet (100).

According to one embodiment of the invention, the inlet gaseous effluent (100) can be smoke resulting from prior combustion, in particular from an industrial process.

According to one embodiment of the invention, the effluent rich in acid compounds (700) can be stored underground, in particular in oil fields.

According to one embodiment of the invention, said at least one acid gas may comprise at least one of the compounds including carbon dioxide CO ₂ .

According to one embodiment of the invention, the absorbent solution rich in acid compounds (500) and the absorbent solution poor in acid compounds (501) are two states of a solvent identical comprising an amine solution with reactive compounds in aqueous solution, said two solutions containing more or less acidic compounds.

The invention also consists in a system for separating at least one acid gas contained in an inlet gaseous effluent (100) capable of implementing the process according to any one of the variants or combinations of variants of the process described. previously.

In order to illustrate the proposed solution, we rely on a process of CO ₂ absorption by washing with amines. The performances considered are those of the 40% wt. Monoethanolamine (MEA) washing process for CO ₂ capture on typical combustion smoke from a coal-fired thermal power plant. These performances have been observed experimentally.

For each of the cases presented, the characteristics of the flue gas stream to be treated are as follows:

Inlet off-gas conditions (100)

[Table 1] Temperature °C 150 Pressure ATM 1 Dry base volume flow Nm ³ /h 250,000 Reference case : capture of CO ₂ on combustion fumes according to the state of the art, cf. Figure 1 .

For the sake of simplification, the inlet gaseous effluent (100) is considered to be free of impurities such as SOx or NOx. Its oxygen content is about 5% vol on a dry basis. The compositions of the fumes leaving the oven are generally supplied on a dry basis. For the production of these examples, we consider hydrated flue gases at a level of 0.043 kg H ₂ O/kg dry gas (value recovered from a typical combustion flue gas from a coal-fired thermal power plant). Its composition is as follows:

Smoke composition 5% vol of O ₂

[Table 2] Compound dry base wet base % vol dry gas Flow (Nm3/h) Throughput (kg/h) Throughput (kg/h) % weight CO2 14.12 3.53E+04 7.06E+04 7.06E+04 32.30 N2 80.75 2.02E+05 1.28E+05 1.28E+05 58.78 O2 5.13 1.28E+04 1.05E+04 1.05E+04 4.80 H20 0 0 0 9.01E+03 4.12 Total 100 2.50E+05 2.10E+05 2.19E+05 100

The CO ₂ absorber by washing with M EA 40% by weight located in the separation unit (1001) makes it possible to obtain an effluent poor in acid compounds (200) having 90% by weight less CO ₂ . Its composition is presented in the following table:

Composition of smoke after CO ₂ capture at MEA 40%wt

[Table 3] Compound Processed smoke composition Throughput (kg/h) % weight _CO2 7.06E+03 4.55 # ₂ 1.28E+05 82.87 _O2 1.05E+04 6.77 _H2O 9.01E+03 5.81 Total 1.55E+05 100

The regeneration column (1002) requires a regeneration energy of 3.02 GJ/t _{CO2 captured} . In the figure 1 the steam stream from the hot utility (400) enters the regeneration column (1002). This basic case known in the art of the technique does not specify how the vapor is formed but explains the quantity of vapor necessary to capture 90% of the CO2 in the inlet gaseous effluent. The steam flow required as hot utility (400) for the reboiling of the solvent to capture 90% by weight of CO ₂ by capture at MEA 40% by weight is indicated in the following table:

Characteristics of CO ₂ capture by MEA 40% by weight

[Table 4] Inlet gaseous effluent flow (100) kg/h 2.19E+05 Of which CO ₂ flow kg/h 7.06E+04 Captured CO ₂ flow (90% by weight) kg/h 6.36E+04 Energy needed for regeneration GJ/t _{CO2 captured} 3.02 Energy needed for regeneration kJ/h 1.92E+08 Hot utility flow (400) kg/h 8.86E+04

Case according to one embodiment of the invention: control of the oxygen content of an inlet gaseous effluent (100) containing CO ₂ and supply of energy, with preheating of the effluent to be treated, in accordance with the mode of realization of the Figure 3 .

The performances of the device are compared on 3 cases with an inlet gaseous effluent (100) having a dry base oxygen content of 5% vol (same composition as the smoke of the reference case), 10% vol and 15% vol. The compositions of the fumes considered are as follows:

Smoke composition - 3 O ₂ contents tested

[Table 5] Compound Case 5% vol O ₂ Case 10% vol O ₂ Case 15% vol O ₂ Throughput (kg/h) % wt (wet) Throughput (kg/h) % wt (wet) Throughput (kg/h) % wt (wet) _CO2 7.06E+04 32.30 7.06E+04 31.96 7.06E+04 31.64 # ₂ 1.28E+05 58.78 1.21E+05 54.65 1.13E+05 50.53 _O2 1.05E+04 4.80 2.05E+04 9.26 3.07E+04 13.75 _H2O 9.01E+03 4.12 9.11E+03 4.12 9.11E+03 4.08 Total 2.19E+05 100 2.21E+05 100 2.23E+05 100

The fuel (300) used in the device is methane at 7 bar and 25° C. and having a PCI of 5.003.10 ⁴ kJ/kg. Complete combustion with excess oxygen takes place until the oxygen content reaches the value of 2% vol in the smoke stream leaving the combustion device (2000). The target oxygen content is variable but seeks to be minimized so as to obtain a flue gas stream whose oxygen content does not cause excessive degradation of the amine in the separation unit (1001).

The lower the chosen oxygen content, the greater the quantity of energy to be recovered for the production of steam, but this also impacts the quantity of fuel to be consumed. This value can therefore be optimized.

First the inlet gaseous effluent (100), which is initially at 150°C, is heated up to 650°C in a heat exchange device (3000) using the hot and rich effluent into acid compounds (110) at the outlet of the combustion device (2000) as a hot fluid. The temperature of 650°C is higher than the ignition temperature of the fuel (300), here methane, which is 540°C. This ensures combustion of the fuel together with the smoke to be treated. The temperatures observed for the various cases are presented in the following table. The higher the oxygen content in the inlet smoke, the more combustion there will be in the device, therefore a high outlet temperature.

Temperatures around the heat exchange device (3000) [Table 6] Running reference number Temperature Case 5% vol O ₂ Case 10% vol O ₂ Case 15% vol O ₂ Smoke Preheat Cold starter 100 150 150 150 cold outlet 101 650 650 650 Hot starter 110 906.8 1286 1621 hot exit Not shown 448 872.9 1243 Heat recovery, vaporization Hot starter Not shown 448 872.9 1243 hot exit 120 150 150 150 Boiling Feed Water 800 140 140 140 Steam 3.6 bar 410 140 140 140

The stream of smoke leaving the combustion device (2000) which made it possible to preheat the smoke to be treated then makes it possible to produce water vapor by vaporization of "boiling feed water" at 140°C and 3.6 bar ( necessary steam conditions for the steam required to operate the regenerator with 40% wt MEA solvent). This vapor stream is then used as utility hot, high pressure vapor fluid (410) by the regeneration column (1002). The amount of steam produced is related to the amount of energy necessary for the regeneration of the MEA solvent of 3.02 GJ/t CO ₂ captured, itself linked to the quantity of CO ₂ that it is possible to capture by absorption in the separation unit (1001). The performances obtained in the 3 cases are presented in the following table:

Performance of the device according to the 3 cases

[Table 7] Case 5% vol O ₂ Case 10% vol O ₂ Case 15% vol O ₂ Steam flow (410) generated kg/h 3.40E+04 9.08E+04 1.49E+05 Energy available kJ/h 7.37E+07 1.97E+08 3.22E+08 Energy for regeneration GJ/t CO ₂ captured 3.02 CO ₂ flow captured in the separation unit (1001) kg/h 2.44E+04 6.51E+04 1.07E+05 Total CO ₂ flow kg/h 7.47E+04 8.15E+04 8.84E+04 CO ₂ flow avoided kg/h 2.03E+04 5.43E+04 8.88E+04 Possible CO ₂ capture rate % 32.69% 79.94% 120.56% CO ₂ rate avoided % 28.80% 76.85% 125.74% Note: the CO ₂ capture rate takes into account the additional CO ₂ generated by combustion in the combustion device (2000). We speak of CO ₂ rate avoided when we consider the quantity of CO ₂ finally emitted (after combustion device and CO ₂ capture unit) compared to the quantity of CO ₂ which would have been emitted initially without any capture unit.

The higher the oxygen content in the flue gas stream to be treated, the higher the amount of steam produced, according to the invention, by heat recovery from the flue gases, and therefore the higher the CO ₂ capture rate. thanks to the process according to the invention.

Claims (13)

Method for separating at least one acid gas contained in an inlet gaseous effluent (100) comprising at least the following steps: - A cold gaseous effluent rich in acid compounds (120) is brought into contact, in a separation unit (1001), with an absorbent solution poor in acid compounds (501) so as to obtain a gaseous effluent poor in acid compounds ( 200) and an absorbent solution rich in acid compounds (500), - At least a fraction of the absorbent solution rich in acid compounds (500) is regenerated in a regeneration column (1002) so as to obtain an absorbent solution poor in acid compounds (501) and an effluent rich in acid compounds (700) , said absorbent solution poor in acid compounds (501) being used in the step of bringing into contact with said cold effluent rich in acid compounds (120), Characterized in that the separation process further comprises the following steps: - Combustion is carried out, in a combustion device (2000), of the inlet gaseous effluent (100) with a fuel (300), so as to obtain a hot gaseous effluent rich in acid compounds (110), - The hot gaseous effluent rich in acid compounds (110) is cooled in an exchanger (3000) and the cold effluent rich in acid compounds (120) used in the step of bringing it into contact with an absorbent solution is obtained low in acid compounds (501). Process according to claim 1, in which the quality of the hot effluent rich in acid compounds (110) is controlled with the addition, in the combustion device (2000), of at least one supplementary oxidizer (600 ). Method according to one of the preceding claims, which also comprises a step which consists in introducing a fluid in high pressure liquid form (800) into the exchanger (3000) from which a fluid in high pressure vapor form (410) is withdrawn. A method according to claim 3, wherein said fluid in the form of high pressure vapor (410) is used as a source of energy to operate the regeneration column (1002). Process according to Claim 4, in which the quality of the operation of the regeneration column (1002) is checked with the addition of a complementary fluid in the form of high pressure make-up vapor (401). Method according to one of the preceding claims, which also comprises a step which consists in heating the inlet gaseous effluent (100) before introducing it, in the form of hot inlet gaseous effluent (101), into the device combustion (2000). Process according to claim 6, in which the inlet gaseous effluent (100) is reheated by introducing it into the exchanger (3000) from which it emerges in the form of hot inlet gaseous effluent (101). Process according to one of the preceding claims, in which the inlet gaseous effluent (100) is smoke resulting from prior combustion, in particular from an industrial process. Process according to one of the preceding claims, in which the effluent rich in acid compounds (700) is stored underground, in particular in oil fields. Method according to one of the preceding claims, in which the fuel (300) is waste material or biomass. Method according to one of Claims 2 to 10, in which the said at least one auxiliary oxidizer (600) is dioxygen O ₂ . Process according to one of the preceding claims, in which the said at least one acid gas comprises at least one of the compounds including carbon dioxide CO ₂ . System for separating at least one acid gas contained in an inlet gaseous effluent (100) capable of implementing the method according to claims 1 to 12 comprising: - a separation unit (1001) - a regeneration column (1002) - a combustion device (2000) - an exchanger (3000).

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